This invention relates to a circuit arrangement for a motor vehicle headlight having a reflector and/or a lens, a light source coupled to a voltage providing apparatus (or source), an enclosing light-transmissive shield with at least one electrically conductive heating element thereon or therein, and a switching-on apparatus for the heating element.
Such a circuit arrangement for a motor vehicle of this type is known from German Auslegeschrift DE-AS 27 14 781. A motor vehicle headlight has a reflector and a light source which is coupled to a voltage providing circuit. An enclosing light-transmissive shield of the motor vehicle headlight has at least one electrically conductive heating element on or in the light-transmissive shield which is coupled to a switching-on apparatus.
In a headlight whose light source is not continuously on the enclosing light-transmissive shield has a tendency under particular temperature conditions to become coated or to get an ice build-up thereon. The electrical heating apparatus, which here is turned on dependent upon various turn-on conditions, has however a disadvantageous in that when there is a safety-endangering crack in the enclosing light-transmissive shield, such crack is not recognized.
It is an object of this invention to provide a circuit arrangement for a motor vehicle headlight with which, in addition to avoiding a coating and ice build-up in an uncomplicated and cost effective manner, also provides a dependable, safety-increasing, crack monitoring, or inspection, of the light-transmissive shield.